Various aspects of interdisciplinarity in research and how to quantify and measure those.

Interdisciplinary research figures high on today's policy agendas. This short introduction and overview sketches the complexity of defining and mapping the nature of interdisciplinary research (IDR). The paper focuses on the different approaches to IDR and different methods applied in bibliometric studies that allow measuring it. These methods should not only be able to capture quantitative aspects of IDR but also to monitor evolutionary aspects and help answer the question of whether IDR stimulates collaboration and results in larger impact and visibility. Two specific indicators, variety and disparity, are developed, validated and applied to bibliometric data. They enable the visualization of the interdisciplinary nature of research activities at various levels of analysis (both institutional and individual). And, given the longitudinal character of bibliometric data and databases, both indicators allow for mapping time-dependent phenomena and evolutions. Relevant examples based on the literature and recent results from research conducted at the Leuven bibliometrics group of ECOOM (e.g., Glänzel et al., Proceedings of the 18^th International Conference of the International Society of Scientometrics and Informetrics, 453–464, 2021; Huang et al., Proceedings of the 18^th International Conference of the International Society of Scientometrics and Informetrics, 533–538, 2021) are given, and concrete proposals for future research are articulated. [ABSTRACT FROM AUTHOR]